Role of Stress Protein on Bacterial Infection

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All organisms respond to unfavorable conditions such as stressful environment by the rapid and transient acceleration in the synthesis of a group of proteins called the stress proteins. For pathogenic bacteria, the intracellular environment of macrophages is one of the most hostile environments. Therefore, the bacteria in the phagocytes may respond to the hostile stimuli by the expression of the stress proteins, and those pro. teiris may put the intracellular bacteria at advantages in the survival in the phagocytes. To elucidate the role of bacterial stress protein on the survival in the macrophages and expression of virulence, we studied the stress response and the role of stress proteins of Yersinia enterocolitica and Listeria monocytogenes within macrophages after phagocytosis. The results are as follows ; (1) The Y.enterocolitica gsrLAMBDA was identified as essential for protecting cells under both extracellular environmental stress and intracellular stress in macrophages due to phagocytosis. The gsrLAMBDA encodes a basic 49.5 kDa protein which is a periplasmic protease. (2) The GsrA stress protein was induced by macrophage phagocytosis. (3) L.monocylogenes could grow in macrophages without the induction of stress proteins. (4) The dnaK gene was cloned and subjected to the molecular analysis to understand the role of stress protein DnaK for intracellular survival of L.monocylogenes . (5) The DnaK does not largely contribute to the survival of L.inonocytogenes in macrophage cells but is involved in the step of the phagocytosis. From these results, it is speculated that common mechanisms with the stress proteins would contribute to the expression of the bacterial pathogen esis besides the species-specific mechanisms.